Generally the .back-cross method is used for transferring disease resistance character to a good and well adapted variety. The system of alternate back-crossing and selfing goes on till the desired results are obtained. The plants selected from a progeny in F3 are given the number of that progeny and in each generation the selected plant also given a serial number. Thus, the plants selected in F2 are given serial numbers of their parents ( F2 plants). Single seed descent. TOS4. In addition each progeny in F4 and the subsequent generation is assigned the row number of the progeny in the preveious generation from which it was derived. 1) Selection of desirable plants from the segregating population in self- pollinated crops. Desirable types already exist in population. The cross may be simple or complex depending upon the number of selected parents. 5. In case of transfer of male sterile character from one parent to another requires back-cross method. 2. What are the characters Mendel selected for his experiments on pea plant? The F1 generation seeds are space planted and seeds from these plants are harvested in bulk. both stamen and pistil in the same bloom) and readily transfer pollen from the stamen to the pistil with even the gentlest breeze. The number of selected progenies should be reasonable so that preliminary yield trial with 25-100 progenies can be done. (Breedi⦠In this system, the individual plant progenies in each generation are assigned row number, corresponding to their location in the plot. Mass selection ⢠2. 3) The pedigree record must be accurate. Privacy Policy3. Starting from F2 generation onwards the seeds are planted at commercial seed rate and spacing. 8. In some cases, the plant will produce both male and female flowers, like squash or pumpkin plants. Which part of the male reproductive system store the sperm? The pedigree may be defined as a description of the ancestors of an individual and it generally goes back to some distant ancestors. Since cross-pollinated species are naturally hybrid (heterozygous) for many traits and lose vigour as they become purebred (homozygous), a goal of each of these breeding methods is to preserve or restore heterozygosity. ï¶ Mass selection is a method of breeding in which individual plants are selected on the basis of phenotype from a mixed population, their seeds are bulked and used to grow the next generation. Comparison between the transfer of dominant and recessive gene during back- cross method: Quantitative characters are governed by polygenes such as grain size, plant height, maturity time, etc. Generally, each cross is given a number. Method of Plant Breeding in Self Pollinated Plants – Pedigree Methods. 4. Plants provide nectar and pollen as edible rewards to the animals for visiting a flower. The multiple characters can be transferred in a stepwise method. At the end of back-cross programme, F2 is handled like pedigree method. Pedigree breeding is a method of genetic improvement of self-pollinated species in which superior genotypes are selected from segregating generations and proper records of the ancestry of selected plants are maintained in each generation. 3) It is also used in the selection of new superior recombinant typeâs i.e Transgressive breeding. In Pedigree method, a detailed record of the relationship between the selected plants and their progenies is maintained as a result of this each progeny in every generation can be traced back to the F2 plant from which it originated, such record is known as pedigree record or pedigree. Plant species where normal mode of seed set is through a high degree of cross-pollination have characteristic reproductive features and population structure. In F2 generation, 2000-10000 plants are space planted, 100-500 plants are selected and their seeds are harvested separately. The objectives of all these methods are to develop pure line varieties. Back cross method. Individual plants with desirable characteristics are selected; disease and lodging susceptible progenies to be eliminated, and also the progenies with undesirable characters are rejected even from the selected plants. The progenies are evaluated for plant height, lodging, disease resistance, flowering time, maturity time, etc. These isogenic lines are useful for studying the effect of individual genes. Except the characters of disease resistance other characters can also be transferred by the back-cross method. Preliminary yield trial with three or more replications is conducted to identify few superior lines. The parents are selected in this programme as the previous one, only difference is that the rust resistance is a recessive gene controlled character: The recurrent parent is used as female parent and hybridized with the rust resistant donor plant. *Autogamy: Pollen from the anther is deposited on stigma of same flower. Few (1 to 3) back-crosses with F1 allow much heterozygosity to appear, or two or more recurrent parents may be used in back- cross programme to accumulate genes from them into the back-cross progeny. Each progeny should have about 30 or more plants. During this process the record of parents as well as off-springs is kept, for which it is known as pedigree method. If this is the case, moving the pollen from a male flower to the stigma of a female flower is all that is needed. Breeding Self-Pollinated Crops Selection Methods Pure-line Selection Pure-line selection, like mass selection, begins with a heterogeneous population of homozygous plants. 2. Then the rigid selection is done for the character to be transferred. Many environmental factors, disease outbreak, etc., may select out the particular genotype from this bulk population. Share Your Word File
1. 4. ï¶ Pureline refers to the homogenous progeny of a self pollinated homozygous plant. The F1 plants won’t be rust resistant, these will be back-crossed to the recurrent parent. Mass selection method is used to breed a plant with cross-pollination. Methods of mixed (cross) pollination. Since large populations are grown, the transgressive segregants are more likely to appear and there is greater chance of isolation of transgressive segregants in this method. The selection procedure is same as previous year, only if two or more progenies coming from the same F3 progeny are similar and comparable, then only one may be saved and others may be rejected. Seed multiplication and distribution to the farmers are carried out. 2. The disease resistant variety will be the donor parent. The commonly used breeding methods of self-pollinated plants were developed over a century ago in Europe. Back-cross method is useful for production of isogenic lines, i.e., the lines of a crop which are identical in their genotype except for one gene. Mass selection is a simplest, common and oldest method of crop improvement, in which large number of plants of similar phenotype are selected and their seeds are harvested and mixed together to constitute the new variety. This method gives maximum importance on the breeder to use his/her skill and judgement about the selection of plants and progenies. Kinds of Plants That Are Self-Pollinated. F1 plants are back-crossed to variety A, in this generation all the plants are heterozygous for rust resistant character. ⢠In terms of breeding system, self-pollination is an extreme form of inbreeding, ⢠rapidly restores homozygosity of the genotypes in generations following a chance cross- pollination (hybridization) in nature or an artificial hybridization. Breeding Methods in Cross Pollinated Crops The most important methods of breeding cross-pollinated species are (1) mass selection; (2) development of hybrid varieties; and (3) development of synthetic varieties. 7. Plants are selected against rust resistance and also the characters of variety A. Interspecific gene transfer only can be done through this method. As this method requires more time to get the effect of natural selection for developing a new variety and the lack of using any skill of breeder for selection of superior types, this method is less used by the breeder for crop improvement. Three or more rows for each progeny will help in comparison among progenies. Answer Now and help others. During the 20th century planned hybridization between carefully selected parents has become dominant in the breeding of self-pollinated species. Later a technolgy of two-lines using environmental genetic male sterility (EGMS) counting on photoperiod (PGMS) and temperature (TGMS) sensitivity to induce sterility was in practice. Pedigree refers to record of the ancestry of an individual selected plant. This method has been used to a limited extent due to lack of popularity. In the segregating generation one of the two systems of designation may be followed. Inter-varietal Transfer of Quantitative Characters: Grain characters like seed size and shape, earliness, plant height-all can be transferred from one variety to another with the criteria of high heritability. The success of the method is mainly dependent on the skill of the breeder. The seeds are multiplied and distributed to the farmer. principles and procedures of plant breedingin self and cross pollinated crops to develop the high yielding varieties / hybrids 5. 3. The recurrent parent should be the male parent. The rust resistant plants having resemblance with variety A are selected and back-crossed. Pure line selection ⢠3. The method is generally used for handling segregation generation may be grouped into three categories. 3. 1. At this stage, selection is done among the progenies, because there would be no genetic variation within progenies. 5. The selected strain should get multiplied to release as a new variety. This method is well suited for improvement of characters which can be easily identified and simply inherited. E. g F2, F3 etc. Most New Zealand native flowering plants are pollinated by animals most by insects, but some by birds or even bats. Welcome to BiologyDiscussion! Larger back-cross progenies would be needed than in case of transfer of a single character, and also it may take long time as in each step all the desired characters may not get expressed. i) Pedigree Method ii) Bulk Method iii) Back Cross Method. Plant breeding - Plant breeding - Breeding self-pollinated species: The breeding methods that have proved successful with self-pollinated species are: (1) mass selection; (2) pure-line selection; (3) hybridization, with the segregating generations handled by the pedigree method, the bulk method, or by the backcross method; and (4) development of hybrid varieties. After seed set and maturation, the F1 seeds are harvested separately from each plant individually. Recurrent selection was originally developed as a method of breeding in cross pollinated species. Disclaimer Copyright, Share Your Knowledge
What is Pureline â Definition? Procedure for transferring a recessive gene will be different from that of dominant gene, as the recessive gene will be expressed only in homozygous condition. METHOD OF PLANT BREEDING IN SELF POLLINATED CROPS ï±The procedure of selection used for asexually propagated crops is known as clonal selection, since the selected plants are used to produce new clones. Individual plant progenies are grown and subjected to rust resistance test. But there are greater chances of error, since more number are to be recorded. Cultivated sugarcane (Saccharum officincirum) is susceptible to pests and disease, crossed with S. spontanium which is resistant. For interspecific transfer of genes, back-cross method is widely used for crop improvement. 50% of the BC1 plants which are resistant are selected and back-crossed to the recurrent parent, i.e., variety A. BC2-BC5 Generation (Fourth-Seventh Year): In each back-cross generation, segregation would occur for rust resistance. ï¶ The deliberate mixture of isolines, closely related lines or unrelated lines are referred to as multilines, and the method ⦠The transfer will be unsuccessful if the genetic environment of recurrent parent is not suitable for functioning of the gene of desirable character from donor parent. Pedigree method is useful in selection of new superior recombinant types from a hybridization programme. 1) Only important characteristics should be recorded. Individual plant progenies of F8 generation are grown in single or multi-row plots. Thus each progeny can be traced back to the F3 progeny or F2 plants, from which it originated. 2) Only the promising should be included in the record. During the entire operation, a record of the entire parent’s offspring relationship is kept, is known as pedigree record. 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